2019-01-21T23:07:33ZMagnetotransport of vertex frustrated artificial spin ice structureshttps://repository.iitgn.ac.in/handle/123456789/4239
Magnetotransport of vertex frustrated artificial spin ice structures
Sharma, Elysia; Arroo, Daan M.; Ray, Nirat; Cohen, Lesley; Branford, Will; The APS March Meeting 2019, Boston, US
2019-03-04T00:00:00ZStructure and evolution of Indian physics co-authorship networkshttps://repository.iitgn.ac.in/handle/123456789/4232
Structure and evolution of Indian physics co-authorship networks
Singh, Chakresh Kumar; Jolad, Shivakumar
We trace the evolution of Indian physics community from 1919 to 2013 by analyzing the co-authorship network constructed from papers published by authors in India in American Physical Society (APS) journals. We make inferences on India’s contribution to different branches of Physics and identify the most influential Indian physicists at different time periods. The relative contribution of India to global physics publication (research) and its variation across subfields of physics is assessed. We extract the changing collaboration pattern of authors between Indian physicists through various network measures. We study the evolution of Indian physics communities and trace the mean life and stationarity of communities by size in different APS journals. We map the transition of authors between communities of different sizes from 1970 to 2013, capturing their birth, growth, merger and collapse. We find that Indian–Foreign collaborations are increasing at a faster pace compared to the Indian–Indian. We observe that the degree distribution of Indian collaboration networks follows the power law, with distinct patterns between Physical Review A, B and E, and high energy physics journals Physical Review C and D, and Physical Review Letters. In almost every measure, we observe strong structural differences between low-energy and high-energy physics journals.
2019-01-01T00:00:00ZProperties of the binary neutron star merger GW170817https://repository.iitgn.ac.in/handle/123456789/4230
Properties of the binary neutron star merger GW170817
Sengupta, Anand et al.
On August 17, 2017, the Advanced LIGO and Advanced Virgo gravitational-wave detectors observed a low-mass compact binary inspiral. The initial sky localization of the source of the gravitational-wave signal, GW170817, allowed electromagnetic observatories to identify NGC 4993 as the host galaxy. In this work, we improve initial estimates of the binary’s properties, including component masses, spins, and tidal parameters, using the known source location, improved modeling, and recalibrated Virgo data. We extend the range of gravitational-wave frequencies considered down to 23 Hz, compared to 30 Hz in the initial analysis. We also compare results inferred using several signal models, which are more accurate and incorporate additional physical effects as compared to the initial analysis. We improve the localization of the gravitational-wave source to a 90% credible region of
16
deg
2
. We find tighter constraints on the masses, spins, and tidal parameters, and continue to find no evidence for nonzero component spins. The component masses are inferred to lie between 1.00 and
1.89
M
⊙
when allowing for large component spins, and to lie between 1.16 and
1.60
M
⊙
(with a total mass
2.73
+
0.04
−
0.01
M
⊙
) when the spins are restricted to be within the range observed in Galactic binary neutron stars. Using a precessing model and allowing for large component spins, we constrain the dimensionless spins of the components to be less than 0.50 for the primary and 0.61 for the secondary. Under minimal assumptions about the nature of the compact objects, our constraints for the tidal deformability parameter
˜
Λ
are (0,630) when we allow for large component spins, and
300
+
420
−
230
(using a 90% highest posterior density interval) when restricting the magnitude of the component spins, ruling out several equation-of-state models at the 90% credible level. Finally, with LIGO and GEO600 data, we use a Bayesian analysis to place upper limits on the amplitude and spectral energy density of a possible postmerger signal.
2019-01-01T00:00:00ZOvercharging black holes and cosmic censorship in Eddington-inspired Born-Infeld gravityhttps://repository.iitgn.ac.in/handle/123456789/4227
Overcharging black holes and cosmic censorship in Eddington-inspired Born-Infeld gravity
Jana, Soumya; Shaikh, Rajibul; Sarkar, Sudipta
The Eddington-inspired Born-Infeld (EiBI) gravity is a modification of the theory of general relativity inspired by the nonlinear Born-Infeld electrodynamics. The theory is described by a series of higher-curvature terms added to the Einstein-Hilbert action with the parameter
κ. The EiBI gravity has several interesting exact neutral and charged black hole solutions. We study the problem of overcharging extremal black hole solutions of EiBI gravity using a charged test particle to create naked singularity. We show that, unlike general relativity, the overcharging could be possible for a charged extremal black hole in EiBI gravity as long as the matter sector is described by usual Maxwell’s electrodynamics. Once the matter sector is also modified in accordance to the Born-Infeld prescription with the parameter
b, the overcharging is not possible as long as the parameters obey the condition 4
b2≤1.
2018-12-01T00:00:00Z